Part Search

[Mike4020]

I’m looking for the name and purpose of the part that is missing on one of my savage 99’s.
I’m attaching pictures of the intact 99 and the one missing the bolt/clip.

please let me know what this is.
thankshttps://postimg.cc/gallery/MzdYvDD

[Model24]

It’s a locknut. Numrich?

[CalhounRR]

Sear screw nut. Jack First Gun Parts has some reproductions.